1. Field of the Invention
The present application relates generally to an inkjet image forming device and more specifically, to an inkjet image forming device having a supporting portion, such as a platen, suitable for marginless image forming on a recording medium.
2. Description of Related Art
In a known inkjet type image forming device, a recording head is positioned to face a platen and ejects ink onto a recording medium conveyed on the platen in a sub-scanning direction while moving in a main scanning direction perpendicular to the sub-scanning direction. When the image forming device performs marginless image forming, the recording head ejects ink beyond edges of the recording medium, thereby forming an image which reaches the edges of the recording medium, such that there are no margins.
In such marginless image forming, ink that is ejected from the recording head beyond the edges of the recording medium onto the platen may adhere to the platen. When an edge, e.g., a lead edge or a trail edge, of the recording medium is bent over the platen and contacts the adhered ink, the back side of the recording medium may be stained with the ink.
Another known image forming device, such as the image forming device described in Japanese Laid-Open Patent Application No. 2006-35685, is configured to prevent a recording medium from being stained with ink adhered to a platen. In this known image forming device, the platen has upstream ribs and downstream ribs with respect to a recording medium conveying direction, and a marginless recording area is provided between the upstream ribs and the downstream ribs. First ribs, second ribs, and third ribs are formed in the marginless recording area at suitable intervals in a direction perpendicular to the recording medium conveying direction so as to support the lead and trail edges of the recording medium. Grooves are formed between the first, second, and third ribs to extend in the recording medium conveying direction and to communicate with an ink absorber positioned on a bottom plate of the platen.
In this known image forming device, if a distance between a nozzle face and an ink receiving surface defined by the grooves is too great, ink discharged into the grooves may transform into an ink mist and may float above the platen. Ink mist may be generated from the ink that has not yet reached the ink receiving surface after being ejected from the recording head, or may be generated from the ink accumulated on the ink receiving surface. Such ink mist may adhere to and stain the back side of the recording medium.
On the other hand, if the distance between the nozzle face and the ink receiving surface defined by the grooves is reduced to prevent the generation of such ink mist, a lead edge and a trail edge of the recording medium may contact the ink receiving surface. If the ink is accumulated on the ink receiving surface without being drained quickly therefrom, the ink may adhere to and stain the recording medium.